1. Field of the Invention
This invention relates to an impact wire-dot printer, and more particularly, to a printing head of such a printer including actuating devices for driving dot-impact wires or rods comprising, for example, a suction type actuator.
2. Description of the Related Art
Two types of impact wire-dot printing heads are known in the prior art, i.e., an attraction type and a release type. An attraction type impact wire-dot printing head generally comprises a plurality of (e.g., 24) impact dot printing mechanisms regularly arranged to form a printing pattern; each impact dot-printing mechanism comprising an armature made of a magnetic material, and an electromagnet for attracting the armature to drive an impact dot-wire, hereinafter referred to simply as "wire", in the axial direction.
The impact wire-dot printing head known in the prior art generally comprises a plurality of (e.g., 24) impact dot printing mechanisms arranged radially and equi-angularly, and each of the impact dot-printing mechanisms comprises an armature made of a magnetic material, an electromagnet, a dot-wire, and so on. The armature is usually T-shaped and has an outer end projecting toward the respective sides along an "arrangement face". An armature support ring is provided with a pair of recesses into which the respective outer ends of the armature are loosely fit, whereby when the electromagnet is turned on, the armature is attracted thereto and is turned about a fulcrum point to push the wire outward. On the other hand, when the electromagnet is turned off, the armature is returned by a spring.
In the known printing head, however, to eliminate the T-shaped configuration of the armature, and thereby preserve a necessary gap defined between the projections of the outer ends of the adjacent two armatures, the diameter of the printing head must be increased, and thus it is difficult to reduce the size of the printing head and the printer.